Auxiliary vehicle truck



April 27, 1948.

E. H. ETGEN AUXILIARY VEHICLE TRUCK Filed April 17, 1947' 3 Sheets-Sheet 1 54/1452, BY X4;

INVENTOR. 17 f/E/ 6% romv y April 27, 1948.

AUXILIARY VEHICLE TRUCK Filed April 17, 1947 3 Sheets-Sheet 2 INVENTOR.

fume? ffE/V BY A oe 1 E. H. ETGEN 2,440,502

April 27, 1948.

E. H. ETGEN AUXILIARY VEHICLE TRUCK Filed April 17, r 1947 3 Sheets-Sheet 3 v INVENTOR. [Mme A/ f/f/V Patented Apr. 27, 1948 UNITED STATES PATENT OFFICE AUXILIARY VEHICLE TRUCK Elmer H. Etgen, Los Angeles, Calif.

Application April 17, 1947, Serial No. 742,022

This invention relates to trucks or dollies and more particularly to a truck or dolly for support-. ing the front end of a trailer drawn by a draft Vehicle;

The dolly of the present invention provides a truck for supporting the forward portion of a trailer and thus relieves the towing vehicle of a substantial part of the weight of the trailer. Trailers, particularl the so-called house trailers, are becoming increasingly heavy and tend to severely overload the rear portions of present day passenger vehicles. In many instances it has been found necessary to replace the original spring suspension means of the towing vehicle with heavier suspension means capable of taking the load imposed by the trailer. Although the heavier springs will take the loads imposed by the trailer they detract from the riding qualities of the towing vehicle particularly when disengaged from the trailer.

To obviate this difficulty it has been proposed to support the forward portion of the trailer by a wheeled truck or dolly having a coupling device for connecting the trailer to the towing vehicle.

Many of the dollies previously proposed have been fitted with wheels so mounted that they were incapable of turnin and for this reason made difficult conjoint backing of the trailer and towing vehicle.

Other trailer dollies heretofore proposed have been provided with castering wheels or at least Wheels mounted for movement about a vertical axis which obviated much of the difficulties found with dollies having fixed wheels.

Another problem introduced by the adoption of the dollies previously proposed has been the difficulty in mounting the wheels of the same so that they could move vertically in opposite directions relative to each other when road obstacles were encountered. Various types of spring suspensions have been used but have been subject to a number of criticisms. It was found where coil spring units were used to support the Wheels of the dolly that the desired maximum movement of the wheels could only be had if the coil springs were relatively large. Too large a spring rendered the dolly objectionable to many trailer owners and efforts to reduce the size of the springs merely resulted in a reduction of the movement of wheels.

' It has also been proposed to mount the castering wheel units to a dolly through a pair of articulated levers forming the castering arm of the unit, the levers being urged apart by a coil spring which resiliently supported the load car- 19 Claims. (01.280-124) ried by the dolly. This proposal was subject to the above mentioned criticism because of the use of the springs. In addition, as the lever to which the wheel was mounted wasswung through varying arcs during travel of the vehicle the castering angle varied as the road surface varied and consequently the wheels tended to oscillate or shimmy. This difiiculty was also encountered where the wheels were mounted by leaf springs which formed the arm or lever of the castering wheel unit.

In all wheel installations where springs were used the pressure of the wheels against the ground or running surface increased as the wheels moved upwardly over obstacles and decreased as the Wheels dropped into cavities or the like in the surface over which the wheels were run. These changes-in the pressure of the wheels against the surface tended to increase the shock and resultant vibration in both the towing vehicle and trailer. V

The difiiculties experienced in dollies previously used are obviated by the present invention for the wheels of the dolly herein disclosed are suspended by means of a pneumatic unit which perinits the desired Vertical movement of the wheels and yet provides an adequate support for the trailer.

The suspension means of the present invention comprises in the broadest aspects thereof a cylindrical air reservoir which forms a transverse frame member of the dolly as Well as an axle for the castering wheels for it supports at each end a rotatably mounted sleeve carrying the arm of the wheel unit. Movement of the sleeves is restrained and controlled by one or more pneumatic cylinders the pistons of which are operatively connected to the sleeves; Each cylinder is connected by a suitable air conduit to the reservoir so that air may be forced from a cylinder into the reservoir in response to movement of a wheel. Each piston therefore has 'full travel in its cylinder without materially increasing the pressure of the air in the system. Without an increase of the air pressure there is no increase of the pressure of the Wheel against the ground which elim inates the vibration and shock to the trailer as would be had if spring suspension means were used.

Another advantage of the pneumatic suspension of the dolly of the present invention lies in the ease of adjustment of the load carrying factor of the dolly. This'is done by merely changing the pressureof the air within the system and to this end a valve such as supplied with present day pneumatic tires is provided preferably on each cylinder.

The dolly oi the present invention may be formed as part of the original equipment of a trailer or sold as an accessory to a trailer already in use. Where the dolly is formed as part of the original equipment the longitudinally extending frame members of the trailer should be extended forwardly to provide a longer hitch or'dra'w bar than is ordinarily'used. This isftoprovide'cl'ear ance for-the castering'wheels of the-dolly inall positions of the towing vehicle.

Where the dolly is sold as an accessory and to be mounted to a trailer already in use, anexten sion bar is used to provide the clearance desired. This bar should be one which will provide but;one: pivotal connection between the towing vehicle and the trailer to eliminate the'difllculties'had by reason of the movement arm created by aj -hit'ch having two pivotal connections.

Other; features. and. advantages; of. the dolly. of the present. invention will be apparent from. the. following description taken in. connection with. the accompanying drawing in which;

Figure 1 is aperspective view of one; embodiment of. the dolly. of' the present invention. show-. ing the. same mounted toa. trailer. apart of; which isshowninunb-roken lines and a part in broken lines;

Figure 2 is. atopel'evational view of the dolly shown in Figure 1;

Figure 3 is. a vertical. section. taken. through the .cylinder and piston. of the. suspension means of the dolly;

Figure 4. is. a section taken along line 4..4f of Figure-2;

Figure 5 is. a. fragmentary. view in. sections of an end. of. the. cylindrical frame. member of the. dolly forming the reservoir. of theipneumatic suspensionsystem;

Figure 6 is a view similar to Figure 1 but show,-. ing a. modified form of the dolly of. the invention;

Figure 7. is a fragmentary. view of. the cylindricalframesmembershowing the plate used. to secure the dolly. to theirame of the trailer;

Figure sisa view. similar to Figure 1. but showing another. embodiment of the dolly of. the present invention;

Figure 9 isa side elevational view of the caster Wheel. of. theform. of. the dolly shown in. Figure 8; and

Figure 10 is a perspective view. of one embodie ment of the dolly. of the present inventionmounte ed-to a trailer as-an accessory andshowing; the extension member fixed: to the original hitch. of. the trailer, the trailer beingshown in broken lines.

The-dolly of the present invention. in the one. embodiment illustrated comprises,- reterrin now. to-Figure 1 of the drawing,.a tubular frame-member Hiadapted tobe transversely. mountedat the, front end of; a trailer I t. The tubular frame member I0- is to be, secured tothe frame members L2 of the trailer and may, if desired,- be secured in position by directly welding the same to the framemembers I 2. If found desirable a pair of apertured plates L3, as best shown in- Eigure- Z, may. bewelded or other-wise secured to the tubular member H1, which plates mayvin turn bewelded tothe trailer frame members; L2 or secured to; the latter by bolts or other suitable fastening means.

It will be seen; refer-ring now toFisure; 5;.thaeach nd; f e bul memb r fl-isc osed y flanse i n; t threadedsinto the; member: to;

tightly clamp a gasket l5 between the flange thereof and the annular end face of the tubular member ID. It should be noted that the diameter of the flange of the cap is substantially the same as the outer diameter of the tubular member I0.

A sleeve I6 is telescopically mounted for rotational movement on each end of the tubular member ID and is held against inward movement by collars I1 carried by the frame member ID. Although the collars I13 are illustrated as integral with the member Iii obviously they could be formed separately therefrom and then welded or otherwise secured in position thereon.

Toy-hold the sleeves I6 against outward movement, a circular plate [8 is fixed, to each cap l4 bymeansof; abolt or threaded stud i9 centrally carried,by the latter. The diameter of the plates is as'large as orlarger than the outer diameter ofv the sleeves I6 and prevents outward movement of the same while permitting free rotational movement thereof.

Eachsleeve H3 is provided: at; the; outer end thereof with an. arm 2|. which. carries atthe free end thereof a suitable bearing 22 for receiving a spindle. or king,- pin, .not shown, projecting-upwardly from a yoke or fork, 23-. The. yoke .Z3 -is formedwi-th apair of'curved; arms. supportingan. axle 25 carrying a wheel 2.6L As the spindle of. the yokeis freely rotatable in the bearing: 2% the wheelzd'is free tocaster. V p

The. wheels, fitted. with suitable. pneumatic tires, support the forward end. of. the trailer through a suitable suspension unit. whichin, the formof the invention. illustrated in. Eigure l comprises an arm 21- projecting outwardly; from the inner endof'each sleeveifi. The free end, of. each arm 21 rotatably receivesa pin. 28; of a clevis, 29' which carriesa downwardly.. opening.

second clevis 3,4; the pin 3 2 of. which. extends substantially normal to the pin. 28hr the. clevis 2-9. The pins: 32 are rotatably carried. by the opposite ends. of. a lever 33. mounted by. means. of. uitablepin- 34' to. the bifurcated. lower end ofa rod 35 projecting downwardly from. apiston 36l operating, in a cylinder 3.1. The cylinder. is-

supported. a; bracket 38. welded or otherwise secured. tothe tubular frame member- Ill.

The rod.35- is connected to the piston. 36-bya ball and socket connection member 39} sethatthe rod. may. rock'. or pivot slightly relative to the piston 36. The lower. wall of: the; cylinder aswell as the bracket 38 are formed with. aligned, apertures som what larger than the: diameter of.

the rod 35 to permit the rocking-or pivotal mo,- t'ionpf the rod.

The. upper end at the cylinder mustbe air-: tight and to prevent leakage of air. arQ lnd the pistonv some means must: be providedton sealing; the. annular space between the piston. and the. cylinder. This means. may. comprise a. packing. 4.0 carriedby the upper face of the piston-a1: though any means adapted for thepurpose:v may; be used- Where. the packing. 46. is. used, I have found that a. quantity of oil such. as indicated at 4-.lincreases. the, efiiciency. ofthe, packing M} and-servesalso to-lubricate the wallof, the cylin der. To. replenish; the: oili t, anaperture be provided; in the: top wall of the cylinder; to-

- permit a supplyof. oil to be. droppedinto; the

member H! to the end that the cylinder is in communication with the interior of said member. The member I besides serving as a frame memher. as herebefore explained also forms a reservoir which will receive air forced from the cylinder due to movement of the wheels over road hazards.

To permit the air *pressure within the'system to be regulated, the cylinder 3'! carries a pneumatic valve 44 such as supplied with inner tubes of present day pneumatic tires. When it is desired to replenish air lost by leakage or to increase the pressure of the air within the system it is only necessary to introduce air into the cylinder through the valve 44 either by means of a pump or through the usual air supply to be found in all modern garages and service sta-, tions.

It will now be seen that as the sleeves l6 are rotatably carried by the opposite. ends of the tubular frame member Hi the latter forms an axle about which the wheels 26 are free to arcuately move vertically as the trailer is drawn over an uneven surface. Movement of the sleeves l6 and consequently the wheels 26 is resisted by the cylinder and piston through 'the linkage mechanism comprising the interconnected lever 33 and arms 21.

It will be seen that the wheels may move arcuately about the axis of the frame member ID to accommodate any road condition which might be encountered. As the air under pressure in the system is actually carrying the load of the trailer in all positions of the wheels roadsh'ccks are cushioned and absorbed by the air.

In use with the trailer resting on a substantially level surface the wheels will assume a position relative to the sleeves it somewhat as shown in Figure 1 depending on the pressure of the air within the cylinder 31 and reservoir formed by the member III. New should the trailer be drawn over an elevated road hazard extending across the track of the trailer both wheels will be forced upwardly and the sleeves will be rotated in a clockwise direction to swing both arms in the same direction. This movement of the arms 21 will draw the lever 33 upwardly and thus urge the rod 35 and the piston 36 upwardly as viewed in Figure 1.

It should be seen that the wheel suspension system of the present invention permits the wheels to arcuately move vertically a relatively large distance without the necessity of employing a relatively large cylinder. This feature is brought about as the piston is free to move substantially the entire length of the cylinder. In previously proposed dollies in which coil spring units were used the wheels could move only that distance permitted by compression of the spring. As a coilspring can only be compressed to a length generally in the neighborhood of half its normal length, a given cylinder length inthe dolly herein disclosed will permit a relatively larger wheel movement than a coil spring of the same length. This feature of the dolly of the present invention in addition to obviating struc-' tural disadvantages found in spring units, also enhances the appearance of the dolly for the relatively large and bulky spring units of prior dollies rendered such dollies objectionable to many trailer owners.

As will be understood the compressed air within the system cushions the trailer in that jars and shocks caused by traveling over rough surfaced roads are absorbed and in part taken up by the air cushion in effect formed between the stationary and movable parts of the system. The air under pressure will be slightly compressed as it is forced out of the cylinder through the conduit 43 and into the member II] but yet the reaction force urging the wheels against the surface will not be materially increased. .As the reaction force does not materially increase as the wheels swing upwardly, as would be the case where spring suspension units were used, the resultant shock to the dolly and trailer are eliminated. v e T If the trailer should be drawn .over a road hazard which results in upward movement of one wheel and downward movement of the other, the upwardly moving arm 21 will draw one end of the beam 33 upwardly as the downwardly moving arm '27 forces theother end of the beam downwardly to cause the beam to rock about the pin 34. This relative movement of the wheels may be such' that little or no movement of the piston will occur. On the other handshould one wheel move either downwardly or upwardly and the other remain in its normal running position, the piston will be moved relative to the cylinder in accordance with the movement of the moving wheel.

It should be noted that the wheels 26 are carried .by the dolly at the opposite sides thereof and the dolly is of such a size that the wheels thereof willtravel over the road in the same tracks as the draft vehicle and trailer. Thus any road hazard such as an irregularity in the road surface which can be spanned by the draft vehicle can be spanned by the dolly.

As the wheels are free to caster the trailer will easily follow a. turn of the towing vehicle. This facilitates backing of the trailer as should be understood. The caster wheels further tend to eliminate road shocks to the trailer caused by certain road hazards as the wheels are free to turn and accommodate the irregularities in the surface of the road.

To reduce oscillation or shimmying' -of the wheels due to road conditions imposing lateral thrusts against the same, the axis of the spindles or king pins of the caster wheels have been rearwardly inclined at a small angle to the vertical. This position of the spindles has been found to greatly reduce shimmy under normal road conditions.

It has been found advisable to obviate the possibility of shimmy under abnormal road conditions to provide a dampening device for each wh'eel. This device may comprise a conventional hydraulic shock absorbing member 46 having one end connected by means of a suitable pivot pin 4'! to the one end of a link or lever 49, the opposite end of which is fixed to the upper end of the spindle or king pin of the caster wheel. The opposite end of the shock absorbing member 46 is pivotally secured to the sleeve IE or the arm 2|.

The shock absorbing member just described will effectively damp out any oscillations of each caster wheel but yet will allow each wheel to find its own course and caster freely when necessary. It is obvious that means other than a hydraulic shock-absorbing member can be used'to damp out undesirable oscillations of the wheels.

In the form of the invention shown in Figure 6 in which elements identical to those illustrated in the form of the invention shown in the earlier described figures have been given the same reference characters, the walking beam 33 and the Q devises iming the pivotal-connections hetweet th'hemeind'the arms 27 ewe-beet siihstituted for'eireet pivotel eehheotio e between th ehcief-eec hetm'fl and e-rodeiofs 'hietp eisl piston at; eoereti g in a cyii dee-tz. of the two; eyiihder'e" z' -i-so iewhet: smalier 1h siz' thenfthe; singte cylinder; 31 of the previousiy described i'hbodihiht of theihventiqn. I I

rod Eris co nected to itspistoh through a suitable universiti- Joint to hermit some rocking'ih'ovementdf' th rod relative to'the'pietori ehe cylinder. The cylinders 52 are carried or-stip= s V i m r-member t 2 ie nounted for rotatiofi" about" eh exhihhictttedat 64 whichis .ohlique to the Vet'- 'tiezfl. ittliil be een thatthe-e'xis td'ihterseets ported'by brackets hiboite'der otherwisesecu'reit fixed to the frame members if tithe 'tritiler'.

- A- ozidiiit t4 ieecis' from eetch cylinder 52 to a "t cbfihcti fifl BS CHIrie-dhy the cyiiridricel frame member it which, as in the earlierdeseriheqi orm lie-invention is a seetledmember capable of; seitihg as-"anair-reservoir. 'Fhe interiors,- of the cylinders erethus not only-iii communication with-"t'heihterior ofthe member" but-With each other as Weill pneumatic Vet-Ive is carried hy the toh wan of each cyiinder 52 mm seryes the same pur hose as the pheumatic valve 44" of theeaflier'de scribed form of invention. A fine; plug such as the plug 42 closes an opening in the top'w iil of the cylinder foh-rep1e ishirig-oi1 withi the c hhder for augmenting" the see-reflected by the packin earriedhythe piston. v 4

wilt be seen from this embodiment of the invention that the vertical movement o eeeh Wheel will he trahsmit-tedhy' means ofthe sieetes F51 and" the arms through t-liefog'i's to the pistons operating in the 'd'yi'i'riders fli The intteriorsof the two ct iiiidersare connected-tattle eh reservoir femedby-the frame member who thatair forced either cylinder 52 by movemerit u wardly of the wheeieebout thetXis-of the ftamemember twill flow throti'ghthe ach amt- 54 connected into the r'eservoir t'ormedby theframe member.

As the volume of air held by thisresefvoir is large relttiveto the volume ofelir iihove a-piston very tit-tie eohihressioh ofthe air" the-sys teht is had ever thoiig'h hathwhee-1e of the deity sinitiiteheousiy move upwardly over" en tiste'cie oh themed. Thus=et in the earher' described=ehi= bodihieht of the rioliy themed ressure oheech wheel remains siibstsht-ihiigi cohstent reger'a'iessof the position of the Wheels. As hasbeefihrF vihiisfyexplained this reduces; v'ibret'ioh the tfetfler for the toad ismore unifdfhflydistribated over the wheels of the dolly eveh thehgh the treti'ier is being drawn ever 2m"- ui'ievefi shrface.

Ah ahti-shi'rmny devicesh'ch as 'i'hitetretedes need in the fohh of the 'rioHy'ShoWn-ih" Figure i -isel's'o used in this'erhbodimerit to dztlI-ipfiiit undesirabi'eoseillatiohs or the ctt-stiihg Wheels:

Hefeegatih other deihpehihg means courdibe h-sed' It shouldbe' seen thatthe lest describeci m bodiment of the dolly 0f thepres'efit-im/ehthm has the fea-t-uresenumerated for the eetilier' described-former the dolly.

There is s'how'ii in Figure 8 a'stifi further modi= fled embodiment Oftlfie invention, and 'e Ih'ieiitS- to bfoh'ndiff this embodiment identified-t6 those shown the ftn'iof the ifiviition illustrated in Figures 1 t'hriigh fi hehf befi g itifi like Ffer fie characters;

e vert cai; ihie passing through the cehtei hr the-Wheel at a point spac d ab ve the surface efigag'dhy the Wheel, and that this axis h'gag''f the wheel-engaging surface at o point' located forwardly of the vertical" ii'rie passin through the center of thewhe'el. It win thus'he seeh that this forrriof the i vehtionthe teetering" wheels are hiounted in suhstentialiy" the same niehher as is the front Wheel f a'cofitifitiofill" b cycle.

he n the form of the-d ny show ihmeijires' 1 arid 27 the' rotatebly osoillatory sleeves I 6 are formed with 21 pivotally" eohhecteatby clevis-me nbers 29- and 3} to e; heahi' 33"jiivote,lly cohnected intermediate its'ehds to the lower end of a connecting rod fixed to a piston movingi'rit cefitrtllydisposed' cylinder 31. I

v In this form of the invention as in those "earlier described; the load is" in effect carried by the air cushion which also absorbs road shocks" es! wen as uniformly distributes the load of the forwerd= portionbf the trailer evehiy betweefi the two wheel of the (16115.

Iii-e11 forms' of the present ihventieh her toa fore" described thedouy has-beehih'corporeted as an original part of a trailer. Theihvehtiofifis ot to be limited to such an instail ihtic'inior the daily of the present invention may be later" instai'ied one trailer in use: as ainecc'ss'ory. re is shpwhin Fi ure 10 one means'yoheiipedieht' which can b used to'adtpt any embodiment-of the dolly" of the present invention "hereih shown to trailers previously Sold. In the figuferefeired' td-the forwardlyxtendihg frairie members of a trailer ehess isere-ihdieetjed at" the theusuel' sechet-m mber'ior rec iving t eheli fixed'to the rear the towing vehicle is shown at 12. I

"As the caster wheels of the dolls; require 2m creased cleerancehetweeh the trailer" and the towihg vehieie, en e'i'itensio'n bar or hitch 'fiis fitted t'e the V=shet15ed forwardextremity ef' the trainer heme. This; extension her 'or-hitch s'rhztpd'to' eonforr to" the waiter frame tthd is preferehiy formed t sting operation. 'I'he divrgihg alr'rhs of the xthsiorr harezre for'rheci ehglemembers 14; theverticaifiaiigesofwhich may be securely bolted to thesiddfalbs ofthe frame hie ibersot the trailer. The: extension-her is shah; len th thetwhen' the socket carried by the-forward enact the same 'is-ioeked' in hosttieh troiifid the bell ctrrid by" the towih give meteiheht-orthe estehhgwheeises wen ass-15rdtit in cie'atrmce hetwee the ceisterihg' wheei's and the rear port-ion of the towihgvehicie in air relsttiifehosi'ti'ohs'of the hitter.

ir eheiiid: he oted that the socket m mber si tpiieti with railer a a originally used to for h earto-f the cohheet'ioh between-the trailer tthh th tow 'h t'ehicieisriot'used whehthe exbet of the treilei T'hhs" only t e; uhiversaleom heetieh ishidwhen the Socket 15h locked-eighth obviatesthe 'tiiiheulties htta'wit'h previous 'doliies whiehe ihz ethesocketeerhed bythe chats-sis: 6f

the trailer to secure the latter to the dolly and drawn by the towing vehicle but the possibility that the linkage would jackknife, either horizontally or vertically, was great as soon as any compression forces were exerted on the hitch. This rendered it extremely difficult if not impossible whack the trailer by the towing vehicle but more serious yet was the result had when the brakes of the-towing vehicle were applied suddenly and relatively heavy compression forces were exerted on the linkage.

As shown in Figure 10 the dolly is furnished with apertured plates 73 welded or otherwise securely fixed to the tubular frame member ID. The dolly may be secured to the frame members H of the trailer by passing U-bolts Id-around the latter and securely fastening the bolts through the apertures of the plate 13. It will thus be seen that the dolly can be quickly and easily secured to a trailer without the use of special tools or equipment. The only modification necessary to the trailer is the forming of the bolt-receiving openings in the forwardly extending frame members of the trailer for mounting the extension bar 73,

Whether the dolly of the present invention is subsequently mounted to a trailer or incorporated into a trailer as original equipment, the dolly forms a ground engaging, load-carrying member which will remove the weight of the trailer from the rear of the towing vehicle. Other advantages specificall brought out during the description of the various forms of the dolly of the present invention are in most instances to be had in all forms of the dolly.

Although the'now preferred embodiments of the present invention have been illustrated and described herein, it is to be understood that the invention is not to be limited thereto and is susceptible to changes in form and detail within the scope of the appended claims.

I claim:

1. A vehicle truck, including: a hollow, frame member constituting a pneumatic reservoir and adapted to be attached transversely to the forward end of the vehicle; a ground-wheel support rotatably mounted on each end of said member for arcuately-vertical rotation; a ground-engaging wheel carried by each support; and pneumatic cylinder-and-piston means disposed intermediate the ends of said member, and having a volume less than that of said reservoir and motion-connected by its piston means to each of said wheel supports and flow-connected by its cylinder means to said reservoir, whereby to maintain substantially equal the load pressure on each wheel, thereby minimizing lateral and vertical oscillations of the vehicle. a

2. A vehicle truck, including: a hollow frame member constituting a pneumatic reservoir and adapted to be attached transversely to the for-- ward end of the vehicle; a ground-wheelsupport rotatably mounted on each end of said member for arcuately-vertical rotation; a groundengaging wheel carried by each support; and pneumatic cylinder-and-piston means disposed intermediate the ends of said member and substantially mediately of the vehicle and having a pneumatic volume less than that of said reservoir and having its piston-means motion-connected to each of said rotatable wheel supports and its cylinder means flow-connected to said reservoir, whereby to transmit road-shocks laterally inwardly from each end of the truck and absorb, transversely-centrally of the vehicle and in small compass, road-shocks effecting relatively large '10 vertical movements of said wheels while maintaining the load pressure and reaction substan-' tially equal on each wheel, thereby minimizing lateral and vertical oscillations of the vehicle.

3. A vehicle ground-gear unit including: an elongate hollow frame member attachable transversely to the vehicle frame and adapted to serve as a pneumatic receiver and reservoir; a groundwheel unit, including a ground-engaging wheel, movably mounted on each end of said frame member for arcuately-verti'cal oscillation therearound; and pneumatic shock-energy receiving and dissipating means operatively interposed between said wheel-units and said frame member and having its output-end fluid-flow connected to said pneumatic receiver and reservoir and its force-input end pivotally connected to said wheelunits in such geometrical relationship as to vibrationlessly absorb road-shocks from all the wheelunits and suspend the vehicle on the air of said pneumatic means and of said wheel units.

4. A ground-gear unit, including: a hollow, tubular, hermetically-sealed frame and axle member; means for enabling connection of said member transversely across the front end of an auxiliary vehicle; a wheel support rotatably mounted on each end of said tubular member for arcu ately-vertical movement in a plane parallel to the longitudinal axis of the vehicle; a, ground engaging wheel mounted on each support; and pneumatic cylinder-and-piston means disposed intermediate the ends of said tubular member and having a pneumatic volume less than that of said tubular member and having its piston-means mo"- tion-connected to each of said rotatable wheelsup'ports and its cylinder-means flow-connected to said tubular member, whereby to enable permanent or temporary attachment of said unit to I an unstable auxiliary vehicle requiring running and standing support to convert said vehicle into an independent one capable of running stably and vibrationlessly substantially free of lateral shock and vibration.

5. An auxiliary-vehicle truck, including: a hollow transverse frame member constituting a pneumatic reservoir and adapted to be attached to the forward end of said vehicle; a, sleeve telescopically and rotatably mounted on each'end of said member; a ground-engaging wheel supported at the outer end of each of said sleeves for arcuate vertical displacement; pneumatic cylinder-andpiston means supported mediately of said member, said reservoir having a pneumatic volume considerably greater than that of said cylindermeans; motion-transmitting means extending forwardly from the inner end of each. ofsaid sleeves; a connection between each of the lastsaid means and the outer end of said pistonmeans; and-a flow-connection between the opposite end of said cylinder-means and said reservoir, whereby to maintain'the load pressure and reaction substantially equal on each wheel and minimize lateral as well as vertical shocks and oscillations of the vehicle.

6. A vehicle truck, including: a hollow, frame member constituting a pneumatic reservoir and adapted to be attached transversely to the forward end of the vehicle; a round-wheel support rotatably' mounted on each end of said member for arcuately-vertical rotation; a ground-engaging wheel carried by each support; and means for absorbing differential vertical movements of said wheels due to differential road-shocks thereon and including vertically disposed pneumatic piston-and-cylinder means mounted intermediate the ends of said member, motion-transmitting arms extending forwardly from the inner end of each of said rotatable supports, saidpiston-means being :pivotally connected to the forward end of each of'said arms at stations, and through means,

permitting differential transmission thereto of differential road-reactions from eachwheel, said cylinder-means being connected to said reservoir to commonly receive, dissipate and substantially equalize said differential road shocks.

7. In a vehicle ground-gear unit, a transversely extending; frame-member also constituting a pneumatic reservoir; a sleevetelescopically and rotatably mounted oneach end of 'said'member; aground wheel supported by each sleeve; .8 Pneumatic shock-absorbing cylinder vertically mounted on said axle and flow-connected to said reservoir, and including a downwardly-depending force-receiving member; a forwardly-extending arm on the inner end-of each of said sleeves for transmitting vertical ground impacts onwardly towards said force-receiving member; and a walking-beam pivotally connected near its medial portion-to said force-receiving member and pivotally connected at its extremities to said arms, whereby to pneumatically accommodatediiferentialroad-impacts on the respective .wheels and maintain the road pressure and reaction thereof substantially equal.

8. In a vehicle ground-gear unit, laterally I spaced ground wheels; transversely-extending frame-member forming a pneumatic reservoir, a sleeve telescopically and rotatably mounted on each-end of said member; a ground-wheel supported by each sleeve; a pair ofvertlcally disposed, laterally spaced pneumatic cylinders mounted intermediate the ends of said member and flow-connected to-said reservoir, each cylinder including a downwardly-depending force-receiving'member; a forwardly-extending arm on the inner end of-each sleeve; and a pivotal-connection between the outer end of each arm and the lower end of the corresponding force-receivirigmember, whereby to enable excessive loads imposed on one of said cylinders to be pneumatically accommodated by said reservoir andabsorb differential road-impacts on-the respective wheels and maintain the road-pressure andzreaction thereof substantially equal.

' 9. A, Vehicle ground-supporting and running gear comprising a frame member adapted to be transversely mounted tea-vehicle and forming an axle for the ground-engaging wheels of said gear; a-sleeve rotatably mounted on each end of saidlaxle; an arm extending forwardly from near the outer end of eachsleeve; a ground-engaging wheel supported by the free-end of each arm; a single piston-and-cylinder pneumatic shock-absorbing device mounted on said axle intermediate itsuends to extend substantially -vertic-ally; an armiextending forwardly from anotherlocation onieach of said sleeves; a link extending transversely below the ,last saidarms and below said pneumatic device; pivotalconnections between the ends .of said link andthe :forwardextremities of rsaidl-ast named arms; and a pivotallconnece tion betweenathelower end of said piston and the median point; of said link.

10..In :a vehicle groundssupporting and runninggeanspaced ground-engaging units; a ldouble-ended axle therefor; a sleeve rotatably mounted on each end of said axle; an arm extending forwardly from near the .outer end of each, sleeve to a portion ofthe adjacentgroundengaging element; a pair of piston-land-cylinder 12 pneumaticshock-absorbing devices mounted in laterally spaced, vertically extending relationship on the vehicle frame forward of said axle; an arm extending forwardly from the inner end of each of said sleeves; and a pivotal connection between "theouter end of each arm and the lower end of eachpiston, whereby to accommodateand absorb differential vertical road impacts imposed upon said ground-engaging elements.

11. An auxiliary-Vehicle truck, including: a hollow transverse frame member constituting a pneumatic reservoir and adapted to be attached to the forwardend of said-vehicle; a sleeve telescopically and rotatably mounted on each end of said member; a ground-enga ingwheel-supported at the outer end of each of said sleeves for arcuate vertical displacement; a cylinder mounted intermediate the ends of said frame member; a piston operating in said cylinder; a rod having one end articulated to said piston; a beam; means for pivotally connecting the free end of said rod to said beam intermediate the ends thereof; means for pivotally connecting the opposite ends of said beam to said sleeves; and means connecting the interior of said cylinder to said reservoir to constitute the so interconnected cylinderand reservoir a closed pneumatic system inwhich air may be maintainedat an elevated pressure.

12. A ground-gear unit for converting unstable incomplete trailer vehicles requiring standing andrunning support into independent, complete vehiclesrcapable of running and standing on said gear in a laterally and longitudinallystable con dition, comprising: a frame member; means for attaching said frame member to the forward portion of a trailer vehicle so as to extend transversely thereof; .a sleeve telescopically mounted for rotation at each end of said frame member; a forwardly projecting arm carried by the outer end of each of said sleeves; a ground-engaging caster wheel carried by and disposedbeneath the outer end of each arm; and means for yieldably holding said sleeves against rotation; whereby arcuate movement of said wheels about the axes of said sleeves is yieldably resisted as said wheels engage irre ularities in the surface over which said vehicleis drawn.

13. A ground-gear unit for convertingunstable incomplete trailer vehicles requiring standing and runningsupport into independent, complete vehicles capable of running and standing on said gear in a laterally and longitudinally stable condition, comprising: a framemember; means for attaching said frame member to the forward portion of a trailer vehicle so as to extend transversely thereof; a sleeve telescopically mounted for rotation at each .end of said frame member; a forwardly projecting arm carried by the outer end of each of said sleeves; apair of ground engaging, caster wheels; means carried by the outer end of each .arm for supporting a caster wheel forcastering turning movement about an axis inclined rearwardly to the vertical; and means :for yieldably holding saidsleeves against rotation whereby arcuate movement of said wheels about the-axes of said sleeves is yieldably resisted -.as saidv wheels engage irregularities .in the surface .over which said vehicle is drawn.

1 4. .A ground-gear unit for converting unstable incomplete trailer vehicles requiring standing and running support intoindependent, complete vehicles capable of running and standing on said gear in a laterally and longitudinally stable con- 13 dition, comprising: a frame member; means for attaching said frame member to the forward portion of a trailer vehicle so as to extend transversely thereof; a sleeve telescopically mounted for rotation at each end of said frame member; a forwardly projecting arm carried by the outer end of each of said sleeves; a pair of ground-engaging caster wheels; means carried by the outer end of each arm for supporting a caster wheel for castering turning movement about an axis inclined rearwardly to the vertical; means for yieldably holding said sleeves against rotation whereby arcute movement of said wheels about the axes of said sleevesis yieldably resisted as said wheels engage irregularities in the surface over which said vehicle is drawn; and means for resisting turning movements of said caster wheels about said inclined axes for damping oscillations of said caster Wheels.

15. A ground-gear unit for converting unstable incomplete trailer vehicles requiring standing and running support into independent, complete vehicles capable of running and standing on said gear in a laterally and longitudinally stable condition, comprising: a frame member; means for attaching said frame member to the forward portion of a trailer vehicle so as to extend transversely thereof; a pair of caster wheel units, each wheel unit including a normally trailing wheelcarrying yoke, a spindle and a bearing for rotatably supporting said spindle so as to extend upwardly and rearwardly from said yoke; means carried at each end of said frame member for mounting one of said bearings for arcuate movement about the longitudinal axis of said transversely extending frame member; and means for yieldably resisting said arcuate movement of said bearings whereby said caster wheels are. held in engagement with the surface over which said vehicle is drawn and cooperate with said last named means for yieldably supporting the forward portion of said vehicle.

16. A ground-gear unit for converting unstable incomplete trailer vehicles requiring standing and running support into independent, complete vehicles capable of running and standing on said gear in a laterally and longitudinally stable condition, comprising: a frame member; means for attaching said frame member to the forward portion of a trailer vehicle so as to extend transversely thereof; a pair of caster wheel units, each wheel unit including a wheel carrying yoke normally projecting forwardly, a spindle and a bearing for supporting said spindle for turning movement about an axis inclined to the vertical and intersecting a vertical line passing through the center of the wheel at a point spaced above the surface engaged by the wheel, said axis intersecting said surface at a point located forwardly of the intersection of the vertical line passing through the center of the wheel and said surface; means carried at each end of said frame member for mounting one of said bearings for arcuate movement about the longitudinal axis of said transversely extending frame member; and means for yieldably resisting said arcuate movement of said bearings whereby said caster wheels are held in engagement with the surface over which said vehicle is drawn and cooperate with said last named means for yieldably supporting the forward portion of said vehicle.

17. In a vehicle-truck of the nature described: a pair of ground-engaging wheels; a transverse frame-member dually constituting a double-ended axle for supporting said ground wheels and a pneumatic reservoir: means for mounting said wheels on said axle, said means including an elongate sleeve telescopically and rotatably mounted on each end of said axle; means for restraining movement of said sleeves longitudinally of said axle; a pair of pneumatic cylinders; a piston operating in each cylinder; means connecting said cylinders to said axle and establishing. an air passageway between the former and the reservoir formed by the latter; means for maintaining the pressure of the air within said cylinders and reservoir at a desired elevated value; and means for connecting a piston to each sleeve for conjoint movement therewith whereby the air under pressure yieldably resists rotational movement of said sleeves.

18. A ground-gear unit for converting unstable incomplete trailer vehicles requiring standing and running support into independent, complete vehicles capable of running and standing on said gear in a. laterally and longitudinally stable condition, comprising: an elongate, hollow frame member; means for hermetically sealing said member; means for attaching said frame member to the forward portion of said vehicle so as to extend transversely thereof; a sleeve telescopically mounted for rotation at each end of said frame member; a forwardly projecting arm carried by the outer end of each sleeve; a ground engaging caster wheel supported by the outer end of each arm for turning movement about a substantially vertical axis; an arm carried by the inner end of each sleeve and projecting forwardly therefrom; a pair of pneumatic cylinders; means for supporting said cylinders intermediate the ends of said frame member; a piston operating in each cylinder; a rod connected to each piston and projecting downwardly therefrom, means for pivotally interconnecting the free ends of said rods to the free ends of said last named arms; and means connecting the interiors of said cylinders to each other and to the interior of said frame member.

19. A ground-gear unit for converting unstable incomplete trailer vehicles requiring standing and running support into independent, complete vehicles capable of running and standing on said gear in a laterally and longitudinally stable condition, comprising: an elongate, hollow frame member; means for hermetically sealing said member; means for attaching said frame member to the forward portion of said vehicle so as to extend transversely. thereof; a sleeve telescopically mounted for rotation at each end of said frame member; a forwardly projecting arm carried by the outer end of each sleeve; a ground enaging caster wheel supported by the outer end of each arm for turning movement about a substantially vertical axis; an arm carried by the inner end of each sleeve and projecting forwardly therefrom; apneumatic cylinder; a piston operating therein; means interconnecting the interior of said cylinder and the interior of said frame member which forms a reservoir communicating with said cylinder; a rod connected to and projecting downwardly from said piston; an elongate lever; means for pivotally connecting the free end of said rod to said lever intermediate the ends thereof; and means for pivotally interconnecting the outer ends of said lever to the adjacent free ends of said last named arms.

ELMER H. ETGEN'. 

